Puppet users - Sep 2013 - Generating a variable based on the hostname

Hi all,

I''m wondering what would be the best approach to extract a value from
the
hostname. In my case, the hostname contains the type of environment (dev,
int, qa, prod) and I would like to have a variable called $env which
contains will be extracted from such FQDNs:

- vm-role-app-prod-1
- vm-role-app-qa-1
...

I''ve tried using split, but it was not really practical. Any better
idea ?
Short to deploy a custom fact to add this value to the facts..

PS: I''m using Puppet 2.7.21

-- 
Romain PELISSE,
*"The trouble with having an open mind, of course, is that people will
insist on coming along and trying to put things in it" -- Terry Pratchett*
Belaran ins Prussia (blog) <http://blog.wordpress.belaran.eu/>     (...
finally up and running !)

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A custom fact that uses regex to grab the fourth, dash-separated value from the
hostname seems like a good way to go as it would make the $env value accessible
globally.

Alternatively, you can use a selector within your manifests:

$env = $hostname ? {
    /-dev-/   => ''dev'',
    /-int-/     => ''int'',
    /-qa-/    => ''qa'',
    /-prod-/ => ''prod'',
}

-- Peter
> On Sep 27, 2013, at 5:47 AM, Romain Pelisse <belaran@gmail.com>
wrote:
> 
> Hi all,
> 
> I''m wondering what would be the best approach to extract a value
from the hostname. In my case, the hostname contains the type of environment
(dev, int, qa, prod) and I would like to have a variable called $env which
contains will be extracted from such FQDNs:
> 
> - vm-role-app-prod-1
> - vm-role-app-qa-1
> ...
> 
> I''ve tried using split, but it was not really practical. Any
better idea ? Short to deploy a custom fact to add this value to the facts..
> 
> PS: I''m using Puppet 2.7.21
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Hi, 
 you can use fact like,
env.rb
Facter.add("env") do
   setcode do
        Facter::Util::Resolution.exec(''hostname | cut -d"-"
-f4'')
   end
end
I hope this will work fine.

Thanks & Regards,
Sneha More,
NTT DATA GTS, OSS Center, India (Pune)


On Friday, September 27, 2013 3:17:49 PM UTC+5:30, Romain PELISSE
wrote:
>
> Hi all,
>
> I''m wondering what would be the best approach to extract a value
from the
> hostname. In my case, the hostname contains the type of environment (dev, 
> int, qa, prod) and I would like to have a variable called $env which 
> contains will be extracted from such FQDNs: 
>
> - vm-role-app-prod-1
> - vm-role-app-qa-1
> ...
>
> I''ve tried using split, but it was not really practical. Any
better idea ?
> Short to deploy a custom fact to add this value to the facts..
>
> PS: I''m using Puppet 2.7.21
>
> -- 
> Romain PELISSE,
> *"The trouble with having an open mind, of course, is that people will
> insist on coming along and trying to put things in it" -- Terry
Pratchett*
> Belaran ins Prussia (blog) <http://blog.wordpress.belaran.eu/>    
(...
> finally up and running !) 
>
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On Friday, September 27, 2013 4:47:49 AM UTC-5, Romain PELISSE
wrote:
>
> Hi all,
>
> I''m wondering what would be the best approach to extract a value
from the
> hostname. In my case, the hostname contains the type of environment (dev, 
> int, qa, prod) and I would like to have a variable called $env which 
> contains will be extracted from such FQDNs: 
>
> - vm-role-app-prod-1
> - vm-role-app-qa-1
> ...
>
> I''ve tried using split, but it was not really practical. Any
better idea ?
> Short to deploy a custom fact to add this value to the facts..
>
>
I don''t see why a custom fact would be a good implementation of this. 
One
of the regex-based facilities supported by Puppet would be better.  Or 
split() -- what was wrong with that?

Anyway, here''s a way to do exactly what you asked via Puppet''s
built-in
regsubst() function:

$env = regsubst($hostname, ''^vm-role-app-([^-]+)-.*'',
''\1'')

or here''s an alternative that makes different assumptions about the
form of
incoming hostnames:

$env = regsubst($hostname, ''.*-(dev|int|ga|prod)-.*'',
''\1'')


John

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On 27 September 2013 16:17, jcbollinger <John.Bollinger@stjude.org> wrote:
>
>
> On Friday, September 27, 2013 4:47:49 AM UTC-5, Romain PELISSE wrote:
>>
>> Hi all,
>>
>> I''m wondering what would be the best approach to extract a
value from the
>> hostname. In my case, the hostname contains the type of environment
(dev,
>> int, qa, prod) and I would like to have a variable called $env which
>> contains will be extracted from such FQDNs:
>>
>> - vm-role-app-prod-1
>> - vm-role-app-qa-1
>> ...
>>
>> I''ve tried using split, but it was not really practical. Any
better idea
>> ? Short to deploy a custom fact to add this value to the facts..
>>
>>
> I don''t see why a custom fact would be a good implementation of
this.  One
> of the regex-based facilities supported by Puppet would be better.  Or
> split() -- what was wrong with that?
>
> Anyway, here''s a way to do exactly what you asked via
Puppet''s built-in
> regsubst() function:
>
> $env = regsubst($hostname, ''^vm-role-app-([^-]+)-.*'',
''\1'')
>
> or here''s an alternative that makes different assumptions about
the form
> of incoming hostnames:
>
> $env = regsubst($hostname, ''.*-(dev|int|ga|prod)-.*'',
''\1'')
>
>
>
I think a custom fact for it is nice because it makes it accessible outside
of puppet if you want to. And it would also be stored in puppetdb so you
can query for hosts based on that value.

-- 
Erik Dalén

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